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* [Bug c++/102611] New: [C++23] P2128R6 - Multidimensional subscript operator @ 2021-10-05 16:18 mpolacek at gcc dot gnu.org 2021-10-06 13:13 ` [Bug c++/102611] " jakub at gcc dot gnu.org ` (4 more replies) 0 siblings, 5 replies; 6+ messages in thread From: mpolacek at gcc dot gnu.org @ 2021-10-05 16:18 UTC (permalink / raw) To: gcc-bugs https://gcc.gnu.org/bugzilla/show_bug.cgi?id=102611 Bug ID: 102611 Summary: [C++23] P2128R6 - Multidimensional subscript operator Product: gcc Version: unknown Status: UNCONFIRMED Severity: normal Priority: P3 Component: c++ Assignee: unassigned at gcc dot gnu.org Reporter: mpolacek at gcc dot gnu.org Target Milestone: --- See https://wg21.link/p2128r6 ^ permalink raw reply [flat|nested] 6+ messages in thread
* [Bug c++/102611] [C++23] P2128R6 - Multidimensional subscript operator 2021-10-05 16:18 [Bug c++/102611] New: [C++23] P2128R6 - Multidimensional subscript operator mpolacek at gcc dot gnu.org @ 2021-10-06 13:13 ` jakub at gcc dot gnu.org 2021-10-13 14:42 ` jakub at gcc dot gnu.org ` (3 subsequent siblings) 4 siblings, 0 replies; 6+ messages in thread From: jakub at gcc dot gnu.org @ 2021-10-06 13:13 UTC (permalink / raw) To: gcc-bugs https://gcc.gnu.org/bugzilla/show_bug.cgi?id=102611 Jakub Jelinek <jakub at gcc dot gnu.org> changed: What |Removed |Added ---------------------------------------------------------------------------- CC| |jakub at gcc dot gnu.org, | |ppalka at gcc dot gnu.org --- Comment #1 from Jakub Jelinek <jakub at gcc dot gnu.org> --- Maybe during parsing we should represent the ARRAY_REF if either there is no expression (i.e. []) or there are ,s some other way (perhaps NULL for [], either TREE_LIST or TREE_VEC etc. for 2+) and then for builtin array ref if we see a parameter pack, try to expand it and error out on the [] case (or empty pack) and for 2+ case turn it with a deprecation diagnostics into COMPOUND_EXPR(s) (unless from a pack, then error?). And for the overloaded case handle it like call lookup (perhaps with diagnosed backwards compatibility fallback if the expression list would be valid compound expression and lookup would succeed for that compound expression as argument to single operand operator[]). ^ permalink raw reply [flat|nested] 6+ messages in thread
* [Bug c++/102611] [C++23] P2128R6 - Multidimensional subscript operator 2021-10-05 16:18 [Bug c++/102611] New: [C++23] P2128R6 - Multidimensional subscript operator mpolacek at gcc dot gnu.org 2021-10-06 13:13 ` [Bug c++/102611] " jakub at gcc dot gnu.org @ 2021-10-13 14:42 ` jakub at gcc dot gnu.org 2021-10-13 18:24 ` jakub at gcc dot gnu.org ` (2 subsequent siblings) 4 siblings, 0 replies; 6+ messages in thread From: jakub at gcc dot gnu.org @ 2021-10-13 14:42 UTC (permalink / raw) To: gcc-bugs https://gcc.gnu.org/bugzilla/show_bug.cgi?id=102611 --- Comment #2 from Jakub Jelinek <jakub at gcc dot gnu.org> --- Created attachment 51595 --> https://gcc.gnu.org/bugzilla/attachment.cgi?id=51595&action=edit gcc12-P2128R6-WIP.patch Untested WIP, just template handling hasn't been added yet, so it is useful only without templates so far. ^ permalink raw reply [flat|nested] 6+ messages in thread
* [Bug c++/102611] [C++23] P2128R6 - Multidimensional subscript operator 2021-10-05 16:18 [Bug c++/102611] New: [C++23] P2128R6 - Multidimensional subscript operator mpolacek at gcc dot gnu.org 2021-10-06 13:13 ` [Bug c++/102611] " jakub at gcc dot gnu.org 2021-10-13 14:42 ` jakub at gcc dot gnu.org @ 2021-10-13 18:24 ` jakub at gcc dot gnu.org 2021-11-25 7:38 ` cvs-commit at gcc dot gnu.org 2021-11-25 7:42 ` jakub at gcc dot gnu.org 4 siblings, 0 replies; 6+ messages in thread From: jakub at gcc dot gnu.org @ 2021-10-13 18:24 UTC (permalink / raw) To: gcc-bugs https://gcc.gnu.org/bugzilla/show_bug.cgi?id=102611 Jakub Jelinek <jakub at gcc dot gnu.org> changed: What |Removed |Added ---------------------------------------------------------------------------- Attachment #51595|0 |1 is obsolete| | --- Comment #3 from Jakub Jelinek <jakub at gcc dot gnu.org> --- Created attachment 51596 --> https://gcc.gnu.org/bugzilla/attachment.cgi?id=51596&action=edit gcc12-pr102611.patch Updated patch that handles even templates, including pack expansions. ^ permalink raw reply [flat|nested] 6+ messages in thread
* [Bug c++/102611] [C++23] P2128R6 - Multidimensional subscript operator 2021-10-05 16:18 [Bug c++/102611] New: [C++23] P2128R6 - Multidimensional subscript operator mpolacek at gcc dot gnu.org ` (2 preceding siblings ...) 2021-10-13 18:24 ` jakub at gcc dot gnu.org @ 2021-11-25 7:38 ` cvs-commit at gcc dot gnu.org 2021-11-25 7:42 ` jakub at gcc dot gnu.org 4 siblings, 0 replies; 6+ messages in thread From: cvs-commit at gcc dot gnu.org @ 2021-11-25 7:38 UTC (permalink / raw) To: gcc-bugs https://gcc.gnu.org/bugzilla/show_bug.cgi?id=102611 --- Comment #4 from CVS Commits <cvs-commit at gcc dot gnu.org> --- The master branch has been updated by Jakub Jelinek <jakub@gcc.gnu.org>: https://gcc.gnu.org/g:b38c9cf6d570f6c4c1109e00c8b81d82d0f24df3 commit r12-5510-gb38c9cf6d570f6c4c1109e00c8b81d82d0f24df3 Author: Jakub Jelinek <jakub@redhat.com> Date: Thu Nov 25 08:36:20 2021 +0100 c++: Implement C++23 P2128R6 - Multidimensional subscript operator [PR102611] The following patch implements the C++23 Multidimensional subscript operator P2128R6 paper. As C++20 and older only allow a single expression in between []s (albeit for C++20 with a deprecation warning if it is a comma expression) and even in C++23 and for the coming years I think the vast majority of subscript expressions will still have a single expression and even in C++23 it is quite special, as e.g. the builtin operator requires exactly one assignment expression, the patch attempts to optimize for that case and if possible not to slow down that common case (or use more memory for it). So, already during parsing it differentiates between that (uses a single index_exp tree in that case) and the new cases (zero or two+ expressions in the list), for which it sets index_exp to NULL_TREE and uses a releasing_vec instead similarly to how e.g. finish_call_expr uses it. In call.c it introduces new functions build_op_subscript{,_1} which are something in between build_new_op{,_1} and build_op_call{,_1}. The former requires fixed number of arguments (and the patch still uses it for the common case of subscript with exactly one index expression), the latter handles variable number of arguments but is too CALL_EXPR specific and handles various cases that are unnecessary for the subscript. Right now the subscript for 0 or 2+ expressions doesn't need to deal with builtin candidates and so is quite simple. As discussed in the paper, for backwards compatibility, if for 2+ index expressions build_op_subscript fails (called with tf_none) and the expressions together form a valid comma expression (again checked with tf_none), it is used that C++20-ish way with a pedwarn about it, but if even that fails, build_op_subscript is called again with standard complain flags to diagnose it in the new way. And similarly for the builtin case. The -Wcomma-subscript warning used to be enabled by default unless -Wno-deprecated. Since the C/C++98..20 behavior is no longer deprecated, but ill-formed or changed meaning, it is now for C++23 enabled by default regardless of -Wno-deprecated and controls the pedwarn (but not the errors emitted if something wasn't valid before and isn't valid in C++23 either). 2021-11-25 Jakub Jelinek <jakub@redhat.com> PR c++/102611 gcc/ * doc/invoke.texi (-Wcomma-subscript): Document that for -std=c++20 the option isn't enabled by default with -Wno-deprecated but for -std=c++23 it is. gcc/c-family/ * c-opts.c (c_common_post_options): Enable -Wcomma-subscript by default for C++23 regardless of warn_deprecated. * c-cppbuiltin.c (c_cpp_builtins): Predefine __cpp_multidimensional_subscript=202110L for C++23. gcc/cp/ * cp-tree.h (build_op_subscript): Implement P2128R6 - Multidimensional subscript operator. Declare. (class releasing_vec): Add release method. (grok_array_decl): Remove bool argument, add vec<tree, va_gc> ** and tsubst_flags_t arguments. (build_min_non_dep_op_overload): Declare another overload. * parser.c (cp_parser_parenthesized_expression_list_elt): New function. (cp_parser_postfix_open_square_expression): Mention C++23 syntax in function comment. For C++23 parse zero or more than one initializer clauses in expression list, adjust grok_array_decl caller. (cp_parser_parenthesized_expression_list): Use cp_parser_parenthesized_expression_list_elt. (cp_parser_builtin_offsetof): Adjust grok_array_decl caller. * decl.c (grok_op_properties): For C++23 don't check number of arguments of operator[]. * decl2.c (grok_array_decl): Remove decltype_p argument, add index_exp_list and complain arguments. If index_exp is NULL, handle *index_exp_list as the subscript expression list. * tree.c (build_min_non_dep_op_overload): New overload. * call.c (add_operator_candidates, build_over_call): Adjust comments for removal of build_new_op_1. (build_op_subscript): New function. * pt.c (tsubst_copy_and_build_call_args): New function. (tsubst_copy_and_build) <case ARRAY_REF>: If second operand is magic CALL_EXPR with ovl_op_identifier (ARRAY_REF) as CALL_EXPR_FN, tsubst CALL_EXPR arguments including expanding pack expressions in it and call grok_array_decl instead of build_x_array_ref. <case CALL_EXPR>: Use tsubst_copy_and_build_call_args. * semantics.c (handle_omp_array_sections_1): Adjust grok_array_decl caller. gcc/testsuite/ * g++.dg/cpp2a/comma1.C: Expect different diagnostics for C++23. * g++.dg/cpp2a/comma3.C: Likewise. * g++.dg/cpp2a/comma4.C: Expect diagnostics for C++23. * g++.dg/cpp2a/comma5.C: Expect different diagnostics for C++23. * g++.dg/cpp23/feat-cxx2b.C: Test __cpp_multidimensional_subscript predefined macro. * g++.dg/cpp23/subscript1.C: New test. * g++.dg/cpp23/subscript2.C: New test. * g++.dg/cpp23/subscript3.C: New test. * g++.dg/cpp23/subscript4.C: New test. * g++.dg/cpp23/subscript5.C: New test. * g++.dg/cpp23/subscript6.C: New test. ^ permalink raw reply [flat|nested] 6+ messages in thread
* [Bug c++/102611] [C++23] P2128R6 - Multidimensional subscript operator 2021-10-05 16:18 [Bug c++/102611] New: [C++23] P2128R6 - Multidimensional subscript operator mpolacek at gcc dot gnu.org ` (3 preceding siblings ...) 2021-11-25 7:38 ` cvs-commit at gcc dot gnu.org @ 2021-11-25 7:42 ` jakub at gcc dot gnu.org 4 siblings, 0 replies; 6+ messages in thread From: jakub at gcc dot gnu.org @ 2021-11-25 7:42 UTC (permalink / raw) To: gcc-bugs https://gcc.gnu.org/bugzilla/show_bug.cgi?id=102611 Jakub Jelinek <jakub at gcc dot gnu.org> changed: What |Removed |Added ---------------------------------------------------------------------------- Resolution|--- |FIXED Assignee|unassigned at gcc dot gnu.org |jakub at gcc dot gnu.org Status|UNCONFIRMED |RESOLVED --- Comment #5 from Jakub Jelinek <jakub at gcc dot gnu.org> --- Now implemented for GCC 12. ^ permalink raw reply [flat|nested] 6+ messages in thread
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